Resistance Temperature Devices (RTDs) are widely used for accurate and stable temperature measurement in industrial and scientific applications.
Construction and Design of RTDs:
RTDs consist of either a metal film deposited on a form or wire-wound resistors encased in a glass-ceramic composite.
The diagram illustrates a three-wire RTD within a stainless steel casing for protection.
The non-inductive platinum coil is wound for efficient thermal conduction and is encapsulated in a ceramic powder for improved heat transfer.
Operation:
The element has three leads to account for voltage drops in the lead wires.
Pure metals exhibit positive electrical resistance that increases linearly with temperature.
Resistance is typically measured using a Wheatstone bridge circuit or by applying a constant current.
Usage Considerations:
RTDs need careful handling to prevent electrical current from heating the sensor and causing inaccurate readings.
These features highlight the precise nature of RTDs and their importance in temperature measurement for various applications due to their sensitivity and accuracy.
